A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine conventionally includes, for example, five major sections: a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section is typically positioned at the inlet section of the engine and includes a fan that induces air from the surrounding environment into the engine and accelerates a portion of this air toward the compressor section. The remaining portion of air induced into the fan section is accelerated into and through a bypass plenum and out the exhaust section.
The compressor section raises the pressure of the air received from the fan section. The compressed air from the compressor section then enters a combustion chamber of the combustor section, where a ring of fuel nozzles injects a steady stream of fuel. The fuel and air mixture is ignited to form combustion gases from which energy is extracted in the turbine section.
Known combustors include inner and outer liners that define the annular combustion chamber. The combustors in gas turbine engines typically operate at relatively high temperatures, including temperatures over 3500° F. Such high temperatures can adversely impact the service life of a combustor. Thus, some form of cooling is typically provided for the combustor. One example of combustor cooling is known as effusion cooling. Effusion cooling involves a matrix of relatively small diameter effusion cooling holes extending through the combustor liners to admit a flow of cooling air. The effusion cooling holes are typically angled relative to a surface of the combustor to generate a cooling film on the inner wall of the liners. This angle also increases the length of the effusion holes through the liners, which increases the surface area from which the cooling flow removes heat from the liner.
Although effusion cooling is generally effective, it does suffer certain drawbacks. For example, one characteristic of effusion cooling is that the film effectiveness may be relatively low at or near upstream sections of the combustor liner. Moreover, the cooling film, once it is sufficiently established, may be interrupted by one or more rows of major combustor orifices, such as dilution holes. As a result, some form of cooling augmentation may be used in the upstream sections of effusion cooled combustor liners and/or at locations downstream of major combustor orifices. Such cooling augmentation can complicate the construction of combustor and increase overall size, weight, and/or costs.
Accordingly, it is desirable to provide for an effusion cooling configuration that exhibits improved film effectiveness at all sections of the combustor. In addition, it is desirable to provide a configuration that does not require one or more forms of cooling augmentation. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.